1
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Bland T, Hirani N, Briggs DC, Rossetto R, Ng K, Taylor IA, McDonald NQ, Zwicker D, Goehring NW. Optimized PAR-2 RING dimerization mediates cooperative and selective membrane binding for robust cell polarity. EMBO J 2024:10.1038/s44318-024-00123-3. [PMID: 38907033 DOI: 10.1038/s44318-024-00123-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 05/01/2024] [Accepted: 05/08/2024] [Indexed: 06/23/2024] Open
Abstract
Cell polarity networks are defined by quantitative features of their constituent feedback circuits, which must be tuned to enable robust and stable polarization, while also ensuring that networks remain responsive to dynamically changing cellular states and/or spatial cues during development. Using the PAR polarity network as a model, we demonstrate that these features are enabled by the dimerization of the polarity protein PAR-2 via its N-terminal RING domain. Combining theory and experiment, we show that dimer affinity is optimized to achieve dynamic, selective, and cooperative binding of PAR-2 to the plasma membrane during polarization. Reducing dimerization compromises positive feedback and robustness of polarization. Conversely, enhanced dimerization renders the network less responsive due to kinetic trapping of PAR-2 on internal membranes and reduced sensitivity of PAR-2 to the anterior polarity kinase, aPKC/PKC-3. Thus, our data reveal a key role for a dynamically oligomeric RING domain in optimizing interaction affinities to support a robust and responsive cell polarity network, and highlight how optimization of oligomerization kinetics can serve as a strategy for dynamic and cooperative intracellular targeting.
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Affiliation(s)
- Tom Bland
- Francis Crick Institute, London, NW1 1AT, UK
- Institute for the Physics of Living Systems, University College London, London, UK
| | | | | | - Riccardo Rossetto
- Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - KangBo Ng
- Francis Crick Institute, London, NW1 1AT, UK
- Institute for the Physics of Living Systems, University College London, London, UK
| | | | - Neil Q McDonald
- Francis Crick Institute, London, NW1 1AT, UK
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, London, WC1E 7HX, UK
| | - David Zwicker
- Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - Nathan W Goehring
- Francis Crick Institute, London, NW1 1AT, UK.
- Institute for the Physics of Living Systems, University College London, London, UK.
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2
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Troost T, Seib E, Airich A, Vüllings N, Necakov A, De Renzis S, Klein T. The meaning of ubiquitylation of the DSL ligand Delta for the development of Drosophila. BMC Biol 2023; 21:260. [PMID: 37974242 PMCID: PMC10655352 DOI: 10.1186/s12915-023-01759-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 11/02/2023] [Indexed: 11/19/2023] Open
Abstract
BACKGROUND Ubiquitylation (ubi) of the intracellular domain of the Notch ligand Delta (Dl) by the E3 ligases Neuralized (Neur) and Mindbomb1 (Mib1) on lysines (Ks) is thought to be essential for the its signalling activity. Nevertheless, we have previously shown that DlK2R-HA, a Dl variant where all Ks in its intracellular domain (ICD) are replaced by the structurally similar arginine (R), still possess weak activity if over-expressed. This suggests that ubi is not absolutely required for Dl signalling. However, it is not known whether the residual activity of DlK2R-HA is an effect of over-expression and, if not, whether DlK2R can provide sufficient activity for the whole development of Drosophila. RESULTS To clarify these issues, we generated and analysed DlattP-DlK2R-HA, a knock-in allele into the Dl locus. Our analysis of this allele reveals that the sole presence of one copy of DlattP-DlK2R-HA can provide sufficient activity for completion of development. It further indicates that while ubi is required for the full activity of Dl in Mib1-dependent processes, it is not essential for Neur-controlled neural development. We identify three modes of Dl signalling that are either dependent or independent of ubi. Importantly, all modes depend on the presence of the endocytic adapter Epsin. During activation of Dl, direct binding of Epsin appears not to be an essential requirement. In addition, our analysis further reveals that the Ks are required to tune down the cis-inhibitory interaction of Dl with Notch. CONCLUSIONS Our results indicate that Dl can activate the Notch pathway without ubi of its ICD. It signals via three modes. Ubi is specifically required for the Mib1-dependent processes and the adjustment of cis-inhibition. In contrast to Mib1, Neur can efficiently activate Dl without ubi. Neur probably acts as an endocytic co-adapter in addition to its role as E3 ligase. Endocytosis, regulated in a ubi-dependent or ubi-independent manner is required for signalling and also suppression of cis-inhibition. The findings clarify the role of ubi of the ligands during Notch signalling.
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Affiliation(s)
- Tobias Troost
- Institute of Genetics, Heinrich-Heine-Universitaet Duesseldorf, Universitaetsstr. 1, 40225, Duesseldorf, Germany
| | - Ekaterina Seib
- Institute of Genetics, Heinrich-Heine-Universitaet Duesseldorf, Universitaetsstr. 1, 40225, Duesseldorf, Germany
| | - Alina Airich
- Institute of Genetics, Heinrich-Heine-Universitaet Duesseldorf, Universitaetsstr. 1, 40225, Duesseldorf, Germany
| | - Nicole Vüllings
- Institute of Genetics, Heinrich-Heine-Universitaet Duesseldorf, Universitaetsstr. 1, 40225, Duesseldorf, Germany
| | - Aleksandar Necakov
- Department of Biological Science, Brock University, 1030, Ontario, L2S3A1, Canada
| | - Stefano De Renzis
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Thomas Klein
- Institute of Genetics, Heinrich-Heine-Universitaet Duesseldorf, Universitaetsstr. 1, 40225, Duesseldorf, Germany.
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3
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Zhang N, Zhang H, Khan LA, Jafari G, Eun Y, Membreno E, Gobel V. The biosynthetic-secretory pathway, supplemented by recycling routes, determines epithelial membrane polarity. SCIENCE ADVANCES 2023; 9:eade4620. [PMID: 37379377 PMCID: PMC10306302 DOI: 10.1126/sciadv.ade4620] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 05/24/2023] [Indexed: 06/30/2023]
Abstract
In prevailing epithelial polarity models, membrane-based polarity cues (e.g., the partitioning-defective PARs) position apicobasal cellular membrane domains. Intracellular vesicular trafficking expands these domains by sorting polarized cargo toward them. How the polarity cues themselves are polarized in epithelia and how sorting confers long-range apicobasal directionality to vesicles is still unclear. Here, a systems-based approach using two-tiered C. elegans genomics-genetics screens identifies trafficking molecules that are not implicated in apical sorting yet polarize apical membrane and PAR complex components. Live tracking of polarized membrane biogenesis indicates that the biosynthetic-secretory pathway, linked to recycling routes, is asymmetrically oriented toward the apical domain during this domain's biosynthesis, and that this directionality is regulated upstream of PARs and independent of polarized target membrane domains. This alternative mode of membrane polarization could offer solutions to open questions in current models of epithelial polarity and polarized trafficking.
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Affiliation(s)
- Nan Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
- Key Laboratory of Zoonosis Research by the Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun 130062, China
| | - Hongjie Zhang
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
- Faculty of Health Sciences, University of Macau, Taipa, Macau, China
| | - Liakot A. Khan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
| | - Gholamali Jafari
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
| | - Yong Eun
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
- Department of Medicine, NYC Health & Hospitals/Harlem, Columbia University, New York, NY, USA
| | - Edward Membreno
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
| | - Verena Gobel
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital for Children, Harvard Medical School, Boston, MA, USA
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4
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Yu CW, Wu YC, Liao VHC. Nanoplastics exposure disrupts circadian rhythm associated with dysfunction of the endolysosomal pathway and autophagy in Caenorhabditis elegans. JOURNAL OF HAZARDOUS MATERIALS 2023; 452:131308. [PMID: 37004444 DOI: 10.1016/j.jhazmat.2023.131308] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 03/15/2023] [Accepted: 03/26/2023] [Indexed: 05/03/2023]
Abstract
Nanoplastics (NPs), an emerging pollutant, have raised great safety concerns due to their widespread applications and continuous release into the environment, which lead to potential human and environmental risks. Recently, polystyrene NPs (100 nm; 100 mg/L) exposure has been reported to disrupt circadian rhythms under five days temperature entrainment and be associated with stress resistance decline in Caenorhabditis elegans. This study explored the possible relationship between circadian rhythm disruption and endocytosis and autophagy under polystyrene NPs exposure in C. elegans. We show that the disrupted circadian rhythm induced by NPs exposure reduced stress resistance via endocytosis and autophagy impairment. Furthermore, we found that most NPs taken up by intestinal cells were localized to early endosomes, late endosomes, and lysosomes and delivered to autophagosomes. In addition, the disruption of circadian rhythm inhibited NPs localization to these organelles. These findings indicate that NPs exposure disrupts circadian rhythm and alters its subcellular trafficking, leading to enhanced toxicity in C. elegans. Our results shed light on the prominent role of NPs exposure in circadian rhythm disruption associated with endocytosis and autophagy impairments, which may be conserved in higher animals such as humans.
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Affiliation(s)
- Chan-Wei Yu
- Department of Bioenvironmental Systems Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 106, Taiwan, ROC
| | - Yi-Chun Wu
- Institute of Molecular and Cellular Biology, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 106, Taiwan, ROC
| | - Vivian Hsiu-Chuan Liao
- Department of Bioenvironmental Systems Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 106, Taiwan, ROC.
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5
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Mutagenesis and structural modeling implicate RME-8 IWN domains as conformational control points. PLoS Genet 2022; 18:e1010296. [DOI: 10.1371/journal.pgen.1010296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 11/08/2022] [Accepted: 10/04/2022] [Indexed: 11/05/2022] Open
Abstract
After endocytosis, transmembrane cargo is differentially sorted into degradative or recycling pathways. This process is facilitated by recruitment into physically distinct degradative or recycling microdomains on the limiting membrane of individual endosomes. Endosomal sorting complexes required for transport (ESCRT) mark the degradative microdomain, while the recycling domain is marked by the retromer complex and associated proteins RME-8 and SNX-1. The separation of endosomal microdomains is also controlled by RME-8 and SNX-1, at least in part via removal of degradative component HRS/HGRS-1 from the recycling microdomain. This activity is likely due to recruitment and activation of chaperone Hsc70 on the endosome by the RME-8 DNAJ domain. To better understand the mechanism of RME-8 function we performed a new phylogenetic analysis of RME-8 and identified new conserved sequence features. In a complementary approach, we performed structure-function analysis that identified the C-terminus as important for microdomain localization and likely substrate binding, while N-terminal sequences beyond the known single N-terminal PH-like domain are important for endosome recruitment. Random mutagenesis identified IWN4, and by analogy IWN3, to be important for the autoinhibitory DNAJ domain binding, with IWN3 playing a critical role in HRS uncoating activity. Combining AlphaFold structural predictions with in vivo mutation analysis of RME-8, we propose a model whereby SNX-1 and the IWN domains control the conformation of RME-8 and hence the productive exposure of the DNAJ domain. Furthermore, we propose that the activation of RME-8 is cyclical, with SNX-1 acting as an activator and a target of RME-8 uncoating activity.
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6
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Structure of the Mon1-Ccz1 complex reveals molecular basis of membrane binding for Rab7 activation. Proc Natl Acad Sci U S A 2022; 119:2121494119. [PMID: 35105815 PMCID: PMC8833172 DOI: 10.1073/pnas.2121494119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/22/2021] [Indexed: 01/02/2023] Open
Abstract
Activation of the GTPase Rab7/Ypt7 by its cognate guanine nucleotide exchange factor (GEF) Mon1-Ccz1 marks organelles such as endosomes and autophagosomes for fusion with lysosomes/vacuoles and degradation of their content. Here, we present a high-resolution cryogenic electron microscopy structure of the Mon1-Ccz1 complex that reveals its architecture in atomic detail. Mon1 and Ccz1 are arranged side by side in a pseudo-twofold symmetrical heterodimer. The three Longin domains of each Mon1 and Ccz1 are triangularly arranged, providing a strong scaffold for the catalytic center of the GEF. At the opposite side of the Ypt7-binding site, a positively charged and relatively flat patch stretches the Longin domains 2/3 of Mon1 and functions as a phosphatidylinositol phosphate-binding site, explaining how the GEF is targeted to membranes. Our work provides molecular insight into the mechanisms of endosomal Rab activation and serves as a blueprint for understanding the function of members of the Tri Longin domain Rab-GEF family.
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7
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A dominant negative variant of RAB5B disrupts maturation of surfactant protein B and surfactant protein C. Proc Natl Acad Sci U S A 2022; 119:2105228119. [PMID: 35121658 PMCID: PMC8832968 DOI: 10.1073/pnas.2105228119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2021] [Indexed: 12/19/2022] Open
Abstract
The Rab5 GTPase functions in early endosome (EE) fusion in the endocytic pathway. Here, we propose that RAB5B also has a noncanonical vesicular fusion function in the regulated secretion pathway that produces mature surfactant proteins SP-B and SP-C in the lung. This function was revealed from investigation of a proband with interstitial lung disease suggestive of a surfactant dysfunction disorder who carried a de novo Asp136His variant in the RAB5B gene. Our modeling in C. elegans provided information on the genetic and cell biological mechanism, and analyses of proband and normal lung biopsies suggested a function for RAB5B and EEs in surfactant protein processing/trafficking. This work indicates that RAB5B p.Asp136His causes a surfactant dysfunction disorder. Pathogenic variants in surfactant proteins SP-B and SP-C cause surfactant deficiency and interstitial lung disease. Surfactant proteins are synthesized as precursors (proSP-B, proSP-C), trafficked, and processed via a vesicular-regulated secretion pathway; however, control of vesicular trafficking events is not fully understood. Through the Undiagnosed Diseases Network, we evaluated a child with interstitial lung disease suggestive of surfactant deficiency. Variants in known surfactant dysfunction disorder genes were not found in trio exome sequencing. Instead, a de novo heterozygous variant in RAB5B was identified in the Ras/Rab GTPases family nucleotide binding domain, p.Asp136His. Functional studies were performed in Caenorhabditis elegans by knocking the proband variant into the conserved position (Asp135) of the ortholog, rab-5. Genetic analysis demonstrated that rab-5[Asp135His] is damaging, producing a strong dominant negative gene product. rab-5[Asp135His] heterozygotes were also defective in endocytosis and early endosome (EE) fusion. Immunostaining studies of the proband’s lung biopsy revealed that RAB5B and EE marker EEA1 were significantly reduced in alveolar type II cells and that mature SP-B and SP-C were significantly reduced, while proSP-B and proSP-C were normal. Furthermore, staining normal lung showed colocalization of RAB5B and EEA1 with proSP-B and proSP-C. These findings indicate that dominant negative–acting RAB5B Asp136His and EE dysfunction cause a defect in processing/trafficking to produce mature SP-B and SP-C, resulting in interstitial lung disease, and that RAB5B and EEs normally function in the surfactant secretion pathway. Together, the data suggest a noncanonical function for RAB5B and identify RAB5B p.Asp136His as a genetic mechanism for a surfactant dysfunction disorder.
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8
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Zhang J, Jiang Z, Shi A. Rab GTPases: The principal players in crafting the regulatory landscape of endosomal trafficking. Comput Struct Biotechnol J 2022; 20:4464-4472. [PMID: 36051867 PMCID: PMC9418685 DOI: 10.1016/j.csbj.2022.08.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Revised: 08/05/2022] [Accepted: 08/07/2022] [Indexed: 11/16/2022] Open
Abstract
After endocytosis, diverse cargos are sorted into endosomes and directed to various destinations, including extracellular macromolecules, membrane lipids, and membrane proteins. Some cargos are returned to the plasma membrane via endocytic recycling. In contrast, others are delivered to the Golgi apparatus through the retrograde pathway, while the rest are transported to late endosomes and eventually to lysosomes for degradation. Rab GTPases are major regulators that ensure cargos are delivered to their proper destinations. Rabs are localized to distinct endosomes and play predominant roles in membrane budding, vesicle formation and motility, vesicle tethering, and vesicle fusion by recruiting effectors. The cascades between Rabs via shared effectors or the recruitment of Rab activators provide an additional layer of spatiotemporal regulation of endocytic trafficking. Notably, several recent studies have indicated that disorders of Rab-mediated endocytic transports are closely associated with diseases such as immunodeficiency, cancer, and neurological disorders.
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9
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Podinovskaia M, Prescianotto-Baschong C, Buser DP, Spang A. A novel live-cell imaging assay reveals regulation of endosome maturation. eLife 2021; 10:e70982. [PMID: 34846303 PMCID: PMC8635980 DOI: 10.7554/elife.70982] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 11/09/2021] [Indexed: 12/12/2022] Open
Abstract
Cell-cell communication is an essential process in life, with endosomes acting as key organelles for regulating uptake and secretion of signaling molecules. Endocytosed material is accepted by the sorting endosome where it either is sorted for recycling or remains in the endosome as it matures to be degraded in the lysosome. Investigation of the endosome maturation process has been hampered by the small size and rapid movement of endosomes in most cellular systems. Here, we report an easy versatile live-cell imaging assay to monitor endosome maturation kinetics, which can be applied to a variety of mammalian cell types. Acute ionophore treatment led to enlarged early endosomal compartments that matured into late endosomes and fused with lysosomes to form endolysosomes. Rab5-to-Rab7 conversion and PI(3)P formation and turn over were recapitulated with this assay and could be observed with a standard widefield microscope. We used this approach to show that Snx1 and Rab11-positive recycling endosome recruitment occurred throughout endosome maturation and was uncoupled from Rab conversion. In contrast, efficient endosomal acidification was dependent on Rab conversion. The assay provides a powerful tool to further unravel various aspects of endosome maturation.
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Affiliation(s)
| | | | | | - Anne Spang
- Biozentrum, University of BaselBaselSwitzerland
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10
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Zhang W, Wang S, Yang C, Hu C, Chen D, Luo Q, He Z, Liao Y, Yao Y, Chen J, He J, Hu J, Xia T, Lin L, Shi A. LET-502/ROCK Regulates Endocytic Recycling by Promoting Activation of RAB-5 in a Distinct Subpopulation of Sorting Endosomes. Cell Rep 2021; 32:108173. [PMID: 32966783 DOI: 10.1016/j.celrep.2020.108173] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 07/17/2020] [Accepted: 08/28/2020] [Indexed: 11/24/2022] Open
Abstract
To explore the mechanism of Rab5/RAB-5 activation during endocytic recycling, we perform a genome-wide RNAi screen and identify a recycling regulator, LET-502/ROCK. LET-502 preferentially interacts with RAB-5(GDP) and activates RABX-5 GEF activity toward RAB-5, presumably by disrupting the self-inhibiting conformation of RABX-5. Furthermore, we find that the concomitant loss of LET-502 and another CED-10 effector, TBC-2/RAB-5-GAP, results in an endosomal buildup of RAB-5, indicating that CED-10 directs TBC-2-mediated RAB-5 inactivation and re-activates RAB-5 via LET-502 afterward. Then, we compare the functional position of LET-502 with that of RME-6/RAB-5-GEF. Loss of LET-502-RABX-5 module or RME-6 leads to diminished RAB-5 presence in spatially distinct endosome groups. We conclude that in the intestine of C. elegans, RAB-5 resides in discrete endosome subpopulations. Under the oversight of CED-10, LET-502 synergizes with RABX-5 to revitalize RAB-5 on a subset of endosomes in the deep cytosol, ensuring the progress of basolateral recycling.
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Affiliation(s)
- Wenjuan Zhang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China; Department of Pathology, Maternal and Child Hospital of Hubei Province, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430070 Hubei, China
| | - Shimin Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Chao Yang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Can Hu
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Dan Chen
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Qian Luo
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Zhen He
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Yuhan Liao
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Yuxin Yao
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Juan Chen
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Jun He
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China
| | - Junbo Hu
- Department of Pathology, Maternal and Child Hospital of Hubei Province, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430070 Hubei, China
| | - Tian Xia
- Department of Informatics Engineering, School of Electronic Information and Communications, Huazhong University of Science and Technology, Wuhan, 430074 Hubei, China
| | - Long Lin
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China.
| | - Anbing Shi
- Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China.
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11
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Wu H, Voeltz GK. Reticulon-3 Promotes Endosome Maturation at ER Membrane Contact Sites. Dev Cell 2021; 56:52-66.e7. [PMID: 33434526 DOI: 10.1016/j.devcel.2020.12.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 09/28/2020] [Accepted: 11/02/2020] [Indexed: 10/22/2022]
Abstract
ER tubules form and maintain membrane contact sites (MCSs) with endosomes. How and why these ER-endosome MCSs persist as endosomes traffic and mature is poorly understood. Here we find that a member of the reticulon protein family, Reticulon-3L (Rtn3L), enriches at ER-endosome MCSs as endosomes mature. We show that this localization is due to the long divergent N-terminal cytoplasmic domain of Rtn3L. We found that Rtn3L is recruited to ER-endosome MCSs by endosomal protein Rab9a, which marks a transition stage between early and late endosomes. Rab9a utilizes an FSV region to recruit Rtn3L via its six LC3-interacting region motifs. Consistent with our localization results, depletion or deletion of RTN3 from cells results in endosome maturation and cargo sorting defects, similar to RAB9A depletion. Together our data identify a tubular ER protein that promotes endosome maturation at ER MCSs.
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Affiliation(s)
- Haoxi Wu
- Department of Molecular, Cellular & Developmental Biology, University of Colorado Boulder, Boulder, CO 80309, USA; Howard Hughes Medical Institute, Boulder, CO 80309, USA
| | - Gia K Voeltz
- Department of Molecular, Cellular & Developmental Biology, University of Colorado Boulder, Boulder, CO 80309, USA; Howard Hughes Medical Institute, Boulder, CO 80309, USA.
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12
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Patel PH, Wilkinson EC, Starke EL, McGimsey MR, Blankenship JT, Barbee SA. Vps54 regulates Drosophila neuromuscular junction development and interacts genetically with Rab7 to control composition of the postsynaptic density. Biol Open 2020; 9:bio053421. [PMID: 32747448 PMCID: PMC7473652 DOI: 10.1242/bio.053421] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/22/2020] [Indexed: 01/04/2023] Open
Abstract
Vps54 is a subunit of the Golgi-associated retrograde protein (GARP) complex, which is involved in tethering endosome-derived vesicles to the trans-Golgi network (TGN). In the wobbler mouse, a model for human motor neuron (MN) disease, reduction in the levels of Vps54 causes neurodegeneration. However, it is unclear how disruption of the GARP complex leads to MN dysfunction. To better understand the role of Vps54 in MNs, we have disrupted expression of the Vps54 ortholog in Drosophila and examined the impact on the larval neuromuscular junction (NMJ). Surprisingly, we show that both null mutants and MN-specific knockdown of Vps54 leads to NMJ overgrowth. Reduction of Vps54 partially disrupts localization of the t-SNARE, Syntaxin-16, to the TGN but has no visible impact on endosomal pools. MN-specific knockdown of Vps54 in MNs combined with overexpression of the small GTPases Rab5, Rab7, or Rab11 suppresses the Vps54 NMJ phenotype. Conversely, knockdown of Vps54 combined with overexpression of dominant negative Rab7 causes NMJ and behavioral abnormalities including a decrease in postsynaptic Dlg and GluRIIB levels without any effect on GluRIIA. Taken together, these data suggest that Vps54 controls larval MN axon development and postsynaptic density composition through a mechanism that requires Rab7.
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Affiliation(s)
- Prajal H Patel
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
| | - Emily C Wilkinson
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
| | - Emily L Starke
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
| | - Malea R McGimsey
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
| | - J Todd Blankenship
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
- Molecular and Cellular Biophysics Program, University of Denver, Denver, CO 80210, USA
| | - Scott A Barbee
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
- Molecular and Cellular Biophysics Program, University of Denver, Denver, CO 80210, USA
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13
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Voss L, Foster OK, Harper L, Morris C, Lavoy S, Brandt JN, Peloza K, Handa S, Maxfield A, Harp M, King B, Eichten V, Rambo FM, Hermann GJ. An ABCG Transporter Functions in Rab Localization and Lysosome-Related Organelle Biogenesis in Caenorhabditis elegans. Genetics 2020; 214:419-445. [PMID: 31848222 PMCID: PMC7017009 DOI: 10.1534/genetics.119.302900] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 12/11/2019] [Indexed: 12/20/2022] Open
Abstract
ABC transporters couple ATP hydrolysis to the transport of substrates across cellular membranes. This protein superfamily has diverse activities resulting from differences in their cargo and subcellular localization. Our work investigates the role of the ABCG family member WHT-2 in the biogenesis of gut granules, a Caenorhabditis elegans lysosome-related organelle. In addition to being required for the accumulation of birefringent material within gut granules, WHT-2 is necessary for the localization of gut granule proteins when trafficking pathways to this organelle are partially disrupted. The role of WHT-2 in gut granule protein targeting is likely linked to its function in Rab GTPase localization. We show that WHT-2 promotes the gut granule association of the Rab32 family member GLO-1 and the endolysosomal RAB-7, identifying a novel function for an ABC transporter. WHT-2 localizes to gut granules where it could play a direct role in controlling Rab localization. Loss of CCZ-1 and GLO-3, which likely function as a guanine nucleotide exchange factor (GEF) for GLO-1, lead to similar disruption of GLO-1 localization. We show that CCZ-1, like GLO-3, is localized to gut granules. WHT-2 does not direct the gut granule association of the GLO-1 GEF and our results point to WHT-2 functioning differently than GLO-3 and CCZ-1 Point mutations in WHT-2 that inhibit its transport activity, but not its subcellular localization, lead to the loss of GLO-1 from gut granules, while other WHT-2 activities are not completely disrupted, suggesting that WHT-2 functions in organelle biogenesis through transport-dependent and transport-independent activities.
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Affiliation(s)
- Laura Voss
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Olivia K Foster
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Logan Harper
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Caitlin Morris
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Sierra Lavoy
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - James N Brandt
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Kimberly Peloza
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Simran Handa
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Amanda Maxfield
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Marie Harp
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Brian King
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | | | - Fiona M Rambo
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Greg J Hermann
- Department of Biology, Lewis & Clark College, Portland, Oregon
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14
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Solinger JA, Rashid HO, Prescianotto-Baschong C, Spang A. FERARI is required for Rab11-dependent endocytic recycling. Nat Cell Biol 2020; 22:213-224. [PMID: 31988382 DOI: 10.1038/s41556-019-0456-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 12/16/2019] [Indexed: 01/22/2023]
Abstract
Endosomal transport is essential for cellular organization and compartmentalization and cell-cell communication. Sorting endosomes provide a crossroads for various trafficking pathways and determine recycling, secretion or degradation of proteins. The organization of these processes requires membrane-tethering factors to coordinate Rab GTPase function with membrane fusion. Here, we report a conserved tethering platform that acts in the Rab11 recycling pathways at sorting endosomes, which we name factors for endosome recycling and Rab interactions (FERARI). The Rab-binding module of FERARI consists of Rab11FIP5 and rabenosyn-5/RABS-5, while the SNARE-interacting module comprises VPS45 and VIPAS39. Unexpectedly, the membrane fission protein EHD1 is also a FERARI component. Thus, FERARI appears to combine fusion activity through the SM protein VPS45 with pinching activity through EHD1 on SNX-1-positive endosomal membranes. We propose that coordination of fusion and pinching through a kiss-and-run mechanism drives cargo at endosomes into recycling pathways.
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Affiliation(s)
| | | | | | - Anne Spang
- Biozentrum, University of Basel, Basel, Switzerland.
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15
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Melcarne C, Lemaitre B, Kurant E. Phagocytosis in Drosophila: From molecules and cellular machinery to physiology. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2019; 109:1-12. [PMID: 30953686 DOI: 10.1016/j.ibmb.2019.04.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Revised: 03/22/2019] [Accepted: 04/01/2019] [Indexed: 05/20/2023]
Abstract
Phagocytosis is an evolutionarily conserved mechanism that plays a key role in both host defence and tissue homeostasis in multicellular organisms. A range of surface receptors expressed on different cell types allow discriminating between self and non-self (or altered) material, thus enabling phagocytosis of pathogens and apoptotic cells. The phagocytosis process can be divided into four main steps: 1) binding of the phagocyte to the target particle, 2) particle internalization and phagosome formation, through remodelling of the plasma membrane, 3) phagosome maturation, and 4) particle destruction in the phagolysosome. In this review, we describe our present knowledge on phagocytosis in the fruit fly Drosophila melanogaster, assessing each of the key steps involved in engulfment of both apoptotic cells and bacteria. We also assess the physiological role of phagocytosis in host defence, development and tissue homeostasis.
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Affiliation(s)
- C Melcarne
- Global Health Institute, School of Life Science, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
| | - B Lemaitre
- Global Health Institute, School of Life Science, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
| | - E Kurant
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Haifa, 34988, Israel.
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16
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Griffin EF, Yan X, Caldwell KA, Caldwell GA. Distinct functional roles of Vps41-mediated neuroprotection in Alzheimer's and Parkinson's disease models of neurodegeneration. Hum Mol Genet 2019; 27:4176-4193. [PMID: 30508205 DOI: 10.1093/hmg/ddy308] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Accepted: 08/21/2018] [Indexed: 12/25/2022] Open
Abstract
Commonalities and, in some cases, pathological overlap between neurodegenerative diseases have led to speculation that targeting of underlying mechanisms might be of potentially shared therapeutic benefit. Alzheimer's disease is characterized by the formation of plaques, composed primarily of the amyloid-β 1-42 (Aβ) peptide in the brain, resulting in neurodegeneration. Previously, we have shown that overexpression of the lysosomal-trafficking protein, human Vps41 (hVps41), is neuroprotective in a transgenic worm model of Parkinson's disease, wherein progressive dopaminergic neurodegeneration is induced by α-synuclein overexpression. Here, we report the results of a systematic comparison of hVps41-mediated neuroprotection between α-synuclein and Aβ in transgenic nematode models of Caenorhabditis elegans. Our results indicate that an ARF-like GTPase gene product, ARL-8, mitigates endocytic Aβ neurodegeneration in a VPS-41-dependent manner, rather than through RAB-7 and AP3 as with α-synuclein. Furthermore, the neuroprotective effect of ARL-8 or hVps41 appears to be dependent on their colocalization and the activity of ARL-8. Additionally, we demonstrate that the LC3 orthologue, LGG-2, plays a critical role in Aβ toxicity with ARL-8. Further analysis of functional effectors of Aβ protein processing via the lysosomal pathway will assist in the elucidation of the underlying mechanism involving VPS-41-mediated neuroprotection. These results reveal functional distinctions in the intracellular management of neurotoxic proteins that serve to better inform the path for development of therapeutic interventions to halt neurodegeneration.
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Affiliation(s)
- Edward F Griffin
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA
| | | | - Kim A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA.,Departments of Neurology and Neurobiology, Center for Neurodegeneration and Experimental Therapeutics, Nathan Shock Center for Research on the Basic Biology of Aging, University of Alabama at Birmingham School of Medicine, Birmingham, AL, USA
| | - Guy A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA.,Departments of Neurology and Neurobiology, Center for Neurodegeneration and Experimental Therapeutics, Nathan Shock Center for Research on the Basic Biology of Aging, University of Alabama at Birmingham School of Medicine, Birmingham, AL, USA
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17
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Hill SE, Kauffman KJ, Krout M, Richmond JE, Melia TJ, Colón-Ramos DA. Maturation and Clearance of Autophagosomes in Neurons Depends on a Specific Cysteine Protease Isoform, ATG-4.2. Dev Cell 2019; 49:251-266.e8. [PMID: 30880001 DOI: 10.1016/j.devcel.2019.02.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Revised: 12/17/2018] [Accepted: 02/12/2019] [Indexed: 12/31/2022]
Abstract
In neurons, defects in autophagosome clearance have been associated with neurodegenerative disease. Yet, the mechanisms that coordinate trafficking and clearance of synaptic autophagosomes are poorly understood. Here, we use genetic screens and in vivo imaging in single neurons of C. elegans to identify mechanisms necessary for clearance of synaptic autophagosomes. We observed that autophagy at the synapse can be modulated in vivo by the state of neuronal activity, that autophagosomes undergo UNC-16/JIP3-mediated retrograde transport, and that autophagosomes containing synaptic material mature in the cell body. Through forward genetic screens, we then determined that autophagosome maturation in the cell body depends on the protease ATG-4.2, but not the related ATG-4.1, and that ATG-4.2 can cleave LGG-1/Atg8/GABARAP from membranes. Our studies revealed that ATG-4.2 is specifically necessary for the maturation and clearance of autophagosomes and that defects in transport and ATG-4.2-mediated maturation genetically interact to enhance abnormal accumulation of autophagosomes in neurons.
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Affiliation(s)
- Sarah E Hill
- Department of Neuroscience, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA; Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Karlina J Kauffman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Mia Krout
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Janet E Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Thomas J Melia
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Daniel A Colón-Ramos
- Department of Neuroscience, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA; Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA; Instituto de Neurobiología, Recinto de Ciencias Médicas, Universidad de Puerto Rico, 201 Blvd del Valle, San Juan 00901, Puerto Rico.
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18
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Morris C, Foster OK, Handa S, Peloza K, Voss L, Somhegyi H, Jian Y, Vo MV, Harp M, Rambo FM, Yang C, Hermann GJ. Function and regulation of the Caenorhabditis elegans Rab32 family member GLO-1 in lysosome-related organelle biogenesis. PLoS Genet 2018; 14:e1007772. [PMID: 30419011 PMCID: PMC6268011 DOI: 10.1371/journal.pgen.1007772] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 11/30/2018] [Accepted: 10/17/2018] [Indexed: 02/07/2023] Open
Abstract
Cell type-specific modifications of conventional endosomal trafficking pathways lead to the formation of lysosome-related organelles (LROs). C. elegans gut granules are intestinally restricted LROs that coexist with conventional degradative lysosomes. The formation of gut granules requires the Rab32 family member GLO-1. We show that the loss of glo-1 leads to the mistrafficking of gut granule proteins but does not significantly alter conventional endolysosome biogenesis. GLO-3 directly binds to CCZ-1 and they both function to promote the gut granule association of GLO-1, strongly suggesting that together, GLO-3 and CCZ-1 activate GLO-1. We found that a point mutation in GLO-1 predicted to spontaneously activate, and function independently of it guanine nucleotide exchange factor (GEF), localizes to gut granules and partially restores gut granule protein localization in ccz-1(-) and glo-3(-) mutants. CCZ-1 forms a heterodimeric complex with SAND-1(MON1), which does not function in gut granule formation, to activate RAB-7 in trafficking pathways to conventional lysosomes. Therefore, our data suggest a model whereby the function of a Rab GEF can be altered by subunit exchange. glo-3(-) mutants, which retain low levels of GLO-3 activity, generate gut granules that lack GLO-1 and improperly accumulate RAB-7 in a SAND-1 dependent process. We show that GLO-1 and GLO-3 restrict the distribution of RAB-7 to conventional endolysosomes, providing insights into the segregation of pathways leading to conventional lysosomes and LROs.
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Affiliation(s)
- Caitlin Morris
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Olivia K. Foster
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Simran Handa
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Kimberly Peloza
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Laura Voss
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Hannah Somhegyi
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Youli Jian
- State Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - My Van Vo
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Marie Harp
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Fiona M. Rambo
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Chonglin Yang
- State Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Greg J. Hermann
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
- * E-mail:
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19
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A C9orf72 ALS/FTD Ortholog Acts in Endolysosomal Degradation and Lysosomal Homeostasis. Curr Biol 2018; 28:1522-1535.e5. [PMID: 29731301 DOI: 10.1016/j.cub.2018.03.063] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 02/18/2018] [Accepted: 03/27/2018] [Indexed: 12/11/2022]
Abstract
The most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is the expansion of a hexanucleotide repeat in a non-coding region of the gene C9orf72. We report that loss-of-function mutations in alfa-1, the Caenorhabditis elegans ortholog of C9orf72, cause a novel phenotypic defect: endocytosed yolk is abnormally released into the extra-embryonic space, resulting in refractile "blobs." The alfa-1 blob phenotype is partially rescued by the expression of the human C9orf72 protein, demonstrating that C9orf72 and alfa-1 function similarly. We show that alfa-1 and R144.5, which we identified from a genetic screen for mutants with the blob phenotype and renamed smcr-8, act in the degradation of endolysosomal content and subsequent lysosome reformation. The alfa-1 abnormality in lysosomal reformation results in a general dysregulation in lysosomal homeostasis, leading to defective degradation of phagosomal and autophagosomal contents. We suggest that, like alfa-1, C9orf72 functions in the degradation of endocytosed material and in the maintenance of lysosomal homeostasis. This previously undescribed function of C9orf72 explains a variety of disparate observations concerning the effects of mutations in C9orf72 and its homologs, including the abnormal accumulation of lysosomes and defective fusion of lysosomes to phagosomes. We suggest that aspects of the pathogenic and clinical features of ALS/FTD caused by C9orf72 mutations, such as altered immune responses, aggregation of autophagy targets, and excessive neuronal excitation, result from a reduction in C9orf72 gene function and consequent abnormalities in lysosomal degradation.
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20
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Colacurcio DJ, Pensalfini A, Jiang Y, Nixon RA. Dysfunction of autophagy and endosomal-lysosomal pathways: Roles in pathogenesis of Down syndrome and Alzheimer's Disease. Free Radic Biol Med 2018; 114:40-51. [PMID: 28988799 PMCID: PMC5748263 DOI: 10.1016/j.freeradbiomed.2017.10.001] [Citation(s) in RCA: 118] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 10/03/2017] [Accepted: 10/04/2017] [Indexed: 12/12/2022]
Abstract
Individuals with Down syndrome (DS) have an increased risk of early-onset Alzheimer's Disease (AD), largely owing to a triplication of the APP gene, located on chromosome 21. In DS and AD, defects in endocytosis and lysosomal function appear at the earliest stages of disease development and progress to widespread failure of intraneuronal waste clearance, neuritic dystrophy and neuronal cell death. The same genetic factors that cause or increase AD risk are also direct causes of endosomal-lysosomal dysfunction, underscoring the essential partnership between this dysfunction and APP metabolites in AD pathogenesis. The appearance of APP-dependent endosome anomalies in DS beginning in infancy and evolving into the full range of AD-related endosomal-lysosomal deficits provides a unique opportunity to characterize the earliest pathobiology of AD preceding the classical neuropathological hallmarks. Facilitating this characterization is the authentic recapitulation of this endosomal pathobiology in peripheral cells from people with DS and in trisomy mouse models. Here, we review current research on endocytic-lysosomal dysfunction in DS and AD, the emerging importance of APP/βCTF in initiating this dysfunction, and the potential roles of additional trisomy 21 genes in accelerating endosomal-lysosomal impairment in DS. Collectively, these studies underscore the growing value of investigating DS to probe the biological origins of AD as well as to understand and ameliorate the developmental disability of DS.
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Affiliation(s)
- Daniel J Colacurcio
- Center for Dementia Research, Nathan S. Kline Institute, Orangeburg, NY 10962, USA; Department of Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA
| | - Anna Pensalfini
- Center for Dementia Research, Nathan S. Kline Institute, Orangeburg, NY 10962, USA; Department of Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA
| | - Ying Jiang
- Center for Dementia Research, Nathan S. Kline Institute, Orangeburg, NY 10962, USA; Department of Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA
| | - Ralph A Nixon
- Center for Dementia Research, Nathan S. Kline Institute, Orangeburg, NY 10962, USA; Department of Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA; Department of Cell Biology, New York University Langone Medical Center, New York, NY 10016, USA.
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21
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Panzica MT, Marin HC, Reymann AC, McNally FJ. F-actin prevents interaction between sperm DNA and the oocyte meiotic spindle in C. elegans. J Cell Biol 2017. [PMID: 28637747 PMCID: PMC5551714 DOI: 10.1083/jcb.201702020] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
After fertilization, interactions between sperm and egg DNA must be prevented before the completion of female meiosis. Panzica et al. show that cortical tethering by F-actin prevents contact between the paternal DNA and the meiotic spindle. Fertilization occurs during female meiosis in most animals, which raises the question of what prevents the sperm DNA from interacting with the meiotic spindle. In this study, we find that Caenorhabditis elegans sperm DNA stays in a fixed position at the opposite end of the embryo from the meiotic spindle while yolk granules are transported throughout the embryo by kinesin-1. In the absence of F-actin, the sperm DNA, centrioles, and organelles were transported as a unit with the yolk granules, resulting in sperm DNA within 2 µm of the meiotic spindle. F-actin imaging revealed a cytoplasmic meshwork that might restrict transport in a size-dependent manner. However, increasing yolk granule size did not slow their velocity, and the F-actin moved with the yolk granules. Instead, sperm contents connect to the cortical F-actin to prevent interaction with the meiotic spindle.
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Affiliation(s)
- Michelle T Panzica
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA
| | - Harold C Marin
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA
| | | | - Francis J McNally
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA
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22
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Architecture and mechanism of the late endosomal Rab7-like Ypt7 guanine nucleotide exchange factor complex Mon1-Ccz1. Nat Commun 2017; 8:14034. [PMID: 28051187 PMCID: PMC5216073 DOI: 10.1038/ncomms14034] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 11/23/2016] [Indexed: 01/21/2023] Open
Abstract
The Mon1–Ccz1 complex (MC1) is the guanine nucleotide exchange factor (GEF) for the Rab GTPase Ypt7/Rab7 and is required for endosomal maturation and fusion at the vacuole/lysosome. Here we present the overall architecture of MC1 from Chaetomium thermophilum, and in combining biochemical studies and mutational analysis in yeast, we identify the domains required for catalytic activity, complex assembly and localization of MC1. The crystal structure of a catalytic MC1 core complex bound to Ypt7 provides mechanistic insight into its function. We pinpoint the determinants that allow for a discrimination of the Rab7-like Ypt7 over the Rab5-like Vps21, which are both located on the same membrane. MC1 shares structural similarities with the TRAPP complex, but employs a novel mechanism to promote nucleotide exchange that utilizes a conserved lysine residue of Ypt7, which is inserted upon MC1 binding into the nucleotide-binding pocket of Ypt7 and contributes to specificity. The Mon1-Ccz1 (MC1) complex is a Rab guanine nucleotide exchange factor (RabGEF) for Ypt7/Rab7 important for endosomal maturation. Here the authors present the biochemical and structural characterization of MC1, elucidating its catalytic mechanism and showing that MC1 represents novel class of RabGEFs.
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23
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Abstract
Small GTPases of the Rab protein family control intracellular vesicular trafficking to allow their communication and maintenance. It is a common strategy for intracellular bacteria to exploit these pathways to shape their respective niches for survival. The subversion of Rabs for the generation of an intracellular environment favoring the pathogen has been described almost exclusively for intracellular bacteria that reside within bacterial containing vacuoles (BCVs). However, less is known about Rab subversion for bacteria that rupture the BCV to reach the host cytoplasm. Here, we provide recent examples of Rab targeting by both groups of intracellular bacteria with a special focus on Shigella, the causative agent of bacillary dysentery. Shigella recruits Rab11, the hallmark of the perinuclear recycling compartment to in situ formed macropinosomes at the entry foci via the bacterial effector IpgD. This leads to efficient BCV rupture and cytosolic escape. We discuss the concept of diverted recycling through host Rab GTPases that emerges as a novel pathogen strategy.
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Affiliation(s)
- Noelia López-Montero
- a Institut Pasteur, Research unit "Dynamics of host-pathogen interactions," Paris , France
| | - Jost Enninga
- a Institut Pasteur, Research unit "Dynamics of host-pathogen interactions," Paris , France
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24
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Gengyo-Ando K, Kage-Nakadai E, Yoshina S, Otori M, Kagawa-Nagamura Y, Nakai J, Mitani S. Distinct roles of the two VPS33 proteins in the endolysosomal system in Caenorhabditis elegans. Traffic 2016; 17:1197-1213. [PMID: 27558849 DOI: 10.1111/tra.12430] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 08/18/2016] [Accepted: 08/18/2016] [Indexed: 02/02/2023]
Abstract
Sec1/Munc-18 (SM) family proteins are essential regulators in intracellular transport in eukaryotic cells. The SM protein Vps33 functions as a core subunit of two tethering complexes, class C core vacuole/endosome tethering (CORVET) and homotypic fusion and vacuole protein sorting (HOPS) in the endocytic pathway in yeast. Metazoan cells possess two Vps33 proteins, VPS33A and VPS33B, but their precise roles remain unknown. Here, we present a comparative analysis of Caenorhabditis elegans null mutants for these proteins. We found that the vps-33.1 (VPS33A) mutants exhibited severe defects in both endocytic function and endolysosomal biogenesis in scavenger cells. Furthermore, vps-33.1 mutations caused endocytosis defects in other tissues, and the loss of maternal and zygotic VPS-33.1 resulted in embryonic lethality. By contrast, vps-33.2 mutants were viable but sterile, with terminally arrested spermatocytes. The spermatogenesis phenotype suggests that VPS33.2 is involved in the formation of a sperm-specific organelle. The endocytosis defect in the vps-33.1 mutant was not restored by the expression of VPS-33.2, which indicates that these proteins have nonredundant functions. Together, our data suggest that VPS-33.1 shares most of the general functions of yeast Vps33 in terms of tethering complexes in the endolysosomal system, whereas VPS-33.2 has tissue/organelle specific functions in C. elegans.
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Affiliation(s)
- Keiko Gengyo-Ando
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan. .,Brain and Body System Science Institute, Saitama University, Saitama, Japan. .,Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
| | - Eriko Kage-Nakadai
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.,The OCU Advanced Research Institute for Natural Science and Technology, Osaka City University, Osaka, Japan
| | - Sawako Yoshina
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Muneyoshi Otori
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Yuko Kagawa-Nagamura
- Brain and Body System Science Institute, Saitama University, Saitama, Japan.,Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Junichi Nakai
- Brain and Body System Science Institute, Saitama University, Saitama, Japan.,Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Shohei Mitani
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.
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25
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Shao X, Liu Y, Yu Q, Ding Z, Qian W, Zhang L, Zhang J, Jiang N, Gui L, Xu Z, Hong Y, Ma Y, Wei Y, Liu X, Jiang C, Zhu M, Li H, Li H. Numb regulates vesicular docking for homotypic fusion of early endosomes via membrane recruitment of Mon1b. Cell Res 2016; 26:593-612. [PMID: 26987402 PMCID: PMC4856763 DOI: 10.1038/cr.2016.34] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 11/17/2015] [Accepted: 01/17/2015] [Indexed: 02/05/2023] Open
Abstract
Numb is an endocytic protein that plays crucial roles in diverse cellular processes such as asymmetric cell division, cell migration and differentiation. However, the molecular mechanism by which Numb regulates endocytic trafficking is poorly understood. Here, we demonstrate that Numb is a docking regulator for homotypic fusion of early endosomes (EEs). Numb depletion causes clustered but unfused EEs, which can be rescued by overexpressing cytosolic Numb 65 and Numb 71 but not plasma membrane-attached Numb 66 or Numb 72. Time-lapse analysis reveals that paired vesicles tend to tether but not fuse with each other in the absence of Numb. We further show that Numb binds to another docking regulator, Mon1b, and is required for the recruitment of cytosolic Mon1b to the EE membrane. Consistent with this, deletion of Mon1b causes similar defects in EE fusion. Our study thus identifies a novel mechanism by which Numb regulates endocytic sorting by mediating EE fusion.
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Affiliation(s)
- Ximing Shao
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
| | - Yi Liu
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
- West China Developmental & Stem Cell Biology Institute, West China Second University Hospital, and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
- Current address: Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Qian Yu
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
- West China Developmental & Stem Cell Biology Institute, West China Second University Hospital, and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Zhihao Ding
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
| | - Wenyu Qian
- West China Developmental & Stem Cell Biology Institute, West China Second University Hospital, and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
- SARITEX Center for Stem Cell Engineering Translational Medicine, Shanghai East Hospital, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai 200123, China
| | - Lei Zhang
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
| | - Jianchao Zhang
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
| | - Nan Jiang
- West China Developmental & Stem Cell Biology Institute, West China Second University Hospital, and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
- Current address: Department of Biology, University of Washington, Seattle, Washington, USA
| | - Linfei Gui
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
| | - Zhiheng Xu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Yang Hong
- Department of Cell Biology & Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Yifan Ma
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
| | - Yanjie Wei
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
| | - Xiaoqing Liu
- SARITEX Center for Stem Cell Engineering Translational Medicine, Shanghai East Hospital, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai 200123, China
| | - Changan Jiang
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
- West China Developmental & Stem Cell Biology Institute, West China Second University Hospital, and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Minyan Zhu
- SARITEX Center for Stem Cell Engineering Translational Medicine, Shanghai East Hospital, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai 200123, China
| | - Hongchang Li
- Shenzhen Key Laboratory for Molecular Biology of Neural Development, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China
| | - Huashun Li
- SARITEX Center for Stem Cell Engineering Translational Medicine, Shanghai East Hospital, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai 200123, China
- ATCG Corp, BioBay, Suzhou Industrial Park, Suzhou, Jiangsu 215123, China
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Barrett A, Hermann GJ. A Caenorhabditis elegans Homologue of LYST Functions in Endosome and Lysosome-Related Organelle Biogenesis. Traffic 2016; 17:515-35. [PMID: 26822177 DOI: 10.1111/tra.12381] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 01/25/2016] [Accepted: 01/25/2016] [Indexed: 01/20/2023]
Abstract
LYST-1 is a Caenorhabditis elegans BEACH domain containing protein (BDCP) homologous to LYST and NBEAL2, BDCPs controlling organelle biogenesis that are implicated in human disease. Unlike the three other BDCPs encoded by C. elegans, mutations in lyst-1 lead to smaller lysosome-related organelles (LROs), smaller lysosomes, increased numbers of LROs and decreased numbers of early endosomes. lyst-1(-) mutations do not obviously disrupt protein trafficking to lysosomes or LROs, however, the formation of gut granules is diminished.
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Affiliation(s)
- Alec Barrett
- Department of Biology, Lewis & Clark College, 0615 SW Palatine Hill Rd., Portland, OR, 97219, USA
| | - Greg J Hermann
- Department of Biology, Lewis & Clark College, 0615 SW Palatine Hill Rd., Portland, OR, 97219, USA
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27
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Sakaguchi A, Sato M, Sato K, Gengyo-Ando K, Yorimitsu T, Nakai J, Hara T, Sato K, Sato K. REI-1 Is a Guanine Nucleotide Exchange Factor Regulating RAB-11 Localization and Function in C. elegans Embryos. Dev Cell 2016; 35:211-21. [PMID: 26506309 DOI: 10.1016/j.devcel.2015.09.013] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 08/18/2015] [Accepted: 09/18/2015] [Indexed: 11/29/2022]
Abstract
The small GTPase Rab11 dynamically changes its location to regulate various cellular processes such as endocytic recycling, secretion, and cytokinesis. However, our knowledge of its upstream regulators is still limited. Here, we identify the RAB-11-interacting protein-1 (REI-1) as a unique family of guanine nucleotide exchange factors (GEFs) for RAB-11 in Caenorhabditis elegans. Although REI-1 and its human homolog SH3-binding protein 5 do not contain any known Rab-GEF domains, they exhibited strong GEF activity toward Rab11 in vitro. In C. elegans, REI-1 is expressed in the germline and co-localizes with RAB-11 on the late-Golgi membranes. The loss of REI-1 specifically impaired the targeting of RAB-11 to the late-Golgi compartment and the recycling endosomes in embryos and further reduced the RAB-11 distribution to the cleavage furrow, which resulted in cytokinesis delay. These results suggest that REI-1 is a GEF specifically regulating the RAB-11 localization and functions in early embryos.
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Affiliation(s)
- Aisa Sakaguchi
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Miyuki Sato
- Laboratory of Molecular Membrane Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Katsuya Sato
- Laboratory of Molecular Membrane Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Keiko Gengyo-Ando
- Brain Science Institute, Saitama University, Saitama, Saitama 338-8570, Japan
| | - Tomohiro Yorimitsu
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Junichi Nakai
- Brain Science Institute, Saitama University, Saitama, Saitama 338-8570, Japan
| | - Taichi Hara
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Ken Sato
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Ken Sato
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan.
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Liu K, Jian Y, Sun X, Yang C, Gao Z, Zhang Z, Liu X, Li Y, Xu J, Jing Y, Mitani S, He S, Yang C. Negative regulation of phosphatidylinositol 3-phosphate levels in early-to-late endosome conversion. J Cell Biol 2016; 212:181-98. [PMID: 26783301 PMCID: PMC4738380 DOI: 10.1083/jcb.201506081] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 12/21/2015] [Indexed: 12/19/2022] Open
Abstract
Phosphatidylinositol 3-phosphate (PtdIns3P) plays a central role in endosome fusion, recycling, sorting, and early-to-late endosome conversion, but the mechanisms that determine how the correct endosomal PtdIns3P level is achieved remain largely elusive. Here we identify two new factors, SORF-1 and SORF-2, as essential PtdIns3P regulators in Caenorhabditis elegans. Loss of sorf-1 or sorf-2 leads to greatly elevated endosomal PtdIns3P, which drives excessive fusion of early endosomes. sorf-1 and sorf-2 function coordinately with Rab switching genes to inhibit synthesis of PtdIns3P, allowing its turnover for endosome conversion. SORF-1 and SORF-2 act in a complex with BEC-1/Beclin1, and their loss causes elevated activity of the phosphatidylinositol 3-kinase (PI3K) complex. In mammalian cells, inactivation of WDR91 and WDR81, the homologs of SORF-1 and SORF-2, induces Beclin1-dependent enlargement of PtdIns3P-enriched endosomes and defective degradation of epidermal growth factor receptor. WDR91 and WDR81 interact with Beclin1 and inhibit PI3K complex activity. These findings reveal a conserved mechanism that controls appropriate PtdIns3P levels in early-to-late endosome conversion.
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Affiliation(s)
- Kai Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. Beijing 100101, China Graduate University of Chinese Academy of Sciences, Beijing 100109, China
| | - Youli Jian
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. Beijing 100101, China
| | - Xiaojuan Sun
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. Beijing 100101, China
| | - Chengkui Yang
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Suzhou 215123, China
| | - Zhiyang Gao
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. Beijing 100101, China
| | - Zhili Zhang
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Suzhou 215123, China
| | - Xuezhao Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. Beijing 100101, China Graduate University of Chinese Academy of Sciences, Beijing 100109, China
| | - Yang Li
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. Beijing 100101, China
| | - Jing Xu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. Beijing 100101, China
| | - Yudong Jing
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. Beijing 100101, China
| | - Shohei Mitani
- Department of Physiology, School of Medicine and Institute for Integrated Medical Sciences, Tokyo Women's Medical University, Shinjuku-ku, Tokyo 162-0054, Japan
| | - Sudan He
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, First Affiliated Hospital and Collaborative Innovation Center of Hematology, Soochow University, Suzhou 215123, China
| | - Chonglin Yang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. Beijing 100101, China
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29
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Genetics of Lipid-Storage Management in Caenorhabditis elegans Embryos. Genetics 2016; 202:1071-83. [PMID: 26773047 DOI: 10.1534/genetics.115.179127] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 01/04/2016] [Indexed: 11/18/2022] Open
Abstract
Lipids play a pivotal role in embryogenesis as structural components of cellular membranes, as a source of energy, and as signaling molecules. On the basis of a collection of temperature-sensitive embryonic lethal mutants, a systematic database search, and a subsequent microscopic analysis of >300 interference RNA (RNAi)-treated/mutant worms, we identified a couple of evolutionary conserved genes associated with lipid storage in Caenorhabditis elegans embryos. The genes include cpl-1 (cathepsin L-like cysteine protease), ccz-1 (guanine nucleotide exchange factor subunit), and asm-3 (acid sphingomyelinase), which is closely related to the human Niemann-Pick disease-causing gene SMPD1. The respective mutant embryos accumulate enlarged droplets of neutral lipids (cpl-1) and yolk-containing lipid droplets (ccz-1) or have larger genuine lipid droplets (asm-3). The asm-3 mutant embryos additionally showed an enhanced resistance against C band ultraviolet (UV-C) light. Herein we propose that cpl-1, ccz-1, and asm-3 are genes required for the processing of lipid-containing droplets in C. elegans embryos. Owing to the high levels of conservation, the identified genes are also useful in studies of embryonic lipid storage in other organisms.
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30
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He Y, Yan H, Hua W, Huang Y, Wang Z. Selection and Validation of Reference Genes for Quantitative Real-time PCR in Gentiana macrophylla. FRONTIERS IN PLANT SCIENCE 2016; 7:945. [PMID: 27446172 PMCID: PMC4925707 DOI: 10.3389/fpls.2016.00945] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 06/14/2016] [Indexed: 05/03/2023]
Abstract
Real time quantitative PCR (RT-qPCR or qPCR) has been extensively applied for analyzing gene expression because of its accuracy, sensitivity, and high throughput. However, the unsuitable choice of reference gene(s) can lead to a misinterpretation of results. We evaluated the stability of 10 candidates - five traditional housekeeping genes (UBC21, GAPC2, EF-1α4, UBQ10, and UBC10) and five novel genes (SAND1, FBOX, PTB1, ARP, and Expressed1) - using the transcriptome data of Gentiana macrophylla. Common statistical algorithms ΔC t, GeNorm, NormFinder, and BestKeeper were run with samples collected from plants under various experimental conditions. For normalizing expression levels from tissues at different developmental stages, GAPC2 and UBC21 had the highest rankings. Both SAND1 and GAPC2 proved to be the optimal reference genes for roots from plants exposed to abiotic stresses while EF-1α4 and SAND1 were optimal when examining expression data from the leaves of stressed plants. Based on a comprehensive ranking of stability under different experimental conditions, we recommend that SAND1 and EF-1α4 are the most suitable overall. In this study, to find a suitable reference gene and its real-time PCR assay for G. macrophylla DNA content quantification, we evaluated three target genes including WRKY30, G10H, and SLS, through qualitative and absolute quantitative PCR with leaves under elicitors stressed experimental conditions. Arbitrary use of reference genes without previous evaluation can lead to a misinterpretation of the data. Our results will benefit future research on the expression of genes related to secoiridoid biosynthesis in this species under different experimental conditions.
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Affiliation(s)
- Yihan He
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal UniversityXi’an, China
- School of Geography and Life Science, Qinghai Normal UniversityXining, China
| | - Hailing Yan
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal UniversityXi’an, China
| | - Wenping Hua
- Department of Life Sciences, Shaanxi XueQian Normal UniversityXi’an, China
| | - Yaya Huang
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal UniversityXi’an, China
| | - Zhezhi Wang
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal UniversityXi’an, China
- *Correspondence: Zhezhi Wang,
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31
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A Presynaptic Regulatory System Acts Transsynaptically via Mon1 to Regulate Glutamate Receptor Levels in Drosophila. Genetics 2015; 201:651-64. [PMID: 26290519 DOI: 10.1534/genetics.115.177402] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 08/10/2015] [Indexed: 11/18/2022] Open
Abstract
Mon1 is an evolutionarily conserved protein involved in the conversion of Rab5 positive early endosomes to late endosomes through the recruitment of Rab7. We have identified a role for Drosophila Mon1 in regulating glutamate receptor levels at the larval neuromuscular junction. We generated mutants in Dmon1 through P-element excision. These mutants are short-lived with strong motor defects. At the synapse, the mutants show altered bouton morphology with several small supernumerary or satellite boutons surrounding a mature bouton; a significant increase in expression of GluRIIA and reduced expression of Bruchpilot. Neuronal knockdown of Dmon1 is sufficient to increase GluRIIA levels, suggesting its involvement in a presynaptic mechanism that regulates postsynaptic receptor levels. Ultrastructural analysis of mutant synapses reveals significantly smaller synaptic vesicles. Overexpression of vglut suppresses the defects in synaptic morphology and also downregulates GluRIIA levels in Dmon1 mutants, suggesting that homeostatic mechanisms are not affected in these mutants. We propose that DMon1 is part of a presynaptically regulated transsynaptic mechanism that regulates GluRIIA levels at the larval neuromuscular junction.
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33
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Mottola G. The complexity of Rab5 to Rab7 transition guarantees specificity of pathogen subversion mechanisms. Front Cell Infect Microbiol 2014; 4:180. [PMID: 25566515 PMCID: PMC4273659 DOI: 10.3389/fcimb.2014.00180] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 12/05/2014] [Indexed: 12/19/2022] Open
Affiliation(s)
- Giovanna Mottola
- UMR MD2, Faculté de Médecine NORD, Aix Marseille University and Institute of Research in Biology of the French Army Marseille, France ; Laboratory of Biochemistry, La Timone University Hospital, Assistance Publique Hôpitaux de Marseille Marseille, France
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34
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Solinger JA, Spang A. Loss of the Sec1/Munc18-family proteins VPS-33.2 and VPS-33.1 bypasses a block in endosome maturation in Caenorhabditis elegans. Mol Biol Cell 2014; 25:3909-25. [PMID: 25273556 PMCID: PMC4244200 DOI: 10.1091/mbc.e13-12-0710] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Evidence is presented for the existence of HOPS and CORVET tethering complexes in metazoans. A role is shown for the SM protein components of tethers in controlling the flux of material through the endosomal system. The end of the life of a transport vesicle requires a complex series of tethering, docking, and fusion events. Tethering complexes play a crucial role in the recognition of membrane entities and bringing them into close opposition, thereby coordinating and controlling cellular trafficking events. Here we provide a comprehensive RNA interference analysis of the CORVET and HOPS tethering complexes in metazoans. Knockdown of CORVET components promoted RAB-7 recruitment to subapical membranes, whereas in HOPS knockdowns, RAB-5 was found also on membrane structures close to the cell center, indicating the RAB conversion might be impaired in the absence of these tethering complexes. Unlike in yeast, metazoans have two VPS33 homologues, which are Sec1/Munc18 (SM)-family proteins involved in the regulation of membrane fusion. We assume that in wild type, each tethering complex contains a specific SM protein but that they may be able to substitute for each other in case of absence of the other. Of importance, knockdown of both SM proteins allowed bypass of the endosome maturation block in sand-1 mutants. We propose a model in which the SM proteins in tethering complexes are required for coordinated flux of material through the endosomal system.
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Affiliation(s)
- Jachen A Solinger
- Growth and Development, Biozentrum, University of Basel, CH-4056 Basel, Switzerland
| | - Anne Spang
- Growth and Development, Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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35
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PKG and NHR-49 signalling co-ordinately regulate short-term fasting-induced lysosomal lipid accumulation in C. elegans. Biochem J 2014; 461:509-20. [PMID: 24854345 DOI: 10.1042/bj20140191] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Lysosomes act as terminal degradation organelles to hydrolyse macromolecules derived from both the extracellular space and the cytoplasm. In Caenorhabditis elegans fasting induces the lysosomal compartment to expand. However, the molecular and cellular mechanisms for this stress response remain largely unclear. In the present study, we find that short-term fasting leads to increased accumulation of polar lipids in lysosomes. The fasting response is co-ordinately regulated by EGL-4, the C. elegans PKG (protein kinase G) orthologue, and nuclear hormone receptor NHR-49. Further results demonstrate that EGL-4 acts in sensory neurons to enhance lysosomal lipid accumulation through inhibiting the DAF-3/SMAD pathway, whereas NHR-49 acts in intestine to inhibit lipids accumulation via activation of IPLA-2 (intracellular membrane-associated calcium-independent phospholipase A2) in cytoplasm and other hydrolases in lysosomes. Remarkably, the lysosomal lipid accumulation is independent of autophagy and RAB-7-mediated endocytosis. Taken together, our results reveal a new mechanism for lysosomal lipid metabolism during the stress response, which may provide new clues for investigations of lysosome function in energy homoeostasis.
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36
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The small GTPase RAB-11 directs polarized exocytosis of the intracellular pathogen N. parisii for fecal-oral transmission from C. elegans. Proc Natl Acad Sci U S A 2014; 111:8215-20. [PMID: 24843160 DOI: 10.1073/pnas.1400696111] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Pathogen exit is a key stage in the spread and propagation of infectious disease, with the fecal-oral route being a common mode of disease transmission. However, it is poorly understood which molecular pathways provide the major modes for intracellular pathogen exit and fecal-oral transmission in vivo. Here, we use the transparent nematode Caenorhabditis elegans to investigate intestinal cell exit and fecal-oral transmission by the natural intracellular pathogen Nematocida parisii, which is a recently identified species of microsporidia. We show that N. parisii exits from polarized host intestinal cells by co-opting the host vesicle trafficking system and escaping into the lumen. Using a genetic screen, we identified components of the host endocytic recycling pathway that are required for N. parisii spore exit via exocytosis. In particular, we show that the small GTPase RAB-11 localizes to apical spores, is required for spore-containing compartments to fuse with the apical plasma membrane, and is required for spore exit. In addition, we find that RAB-11-deficient animals exhibit impaired contagiousness, supporting an in vivo role for this host trafficking factor in microsporidia disease transmission. Altogether, these findings provide an in vivo example of the major mode of exit used by a natural pathogen for disease spread via fecal-oral transmission.
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37
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Cui Y, Zhao Q, Gao C, Ding Y, Zeng Y, Ueda T, Nakano A, Jiang L. Activation of the Rab7 GTPase by the MON1-CCZ1 Complex Is Essential for PVC-to-Vacuole Trafficking and Plant Growth in Arabidopsis. THE PLANT CELL 2014; 26:2080-2097. [PMID: 24824487 PMCID: PMC4079370 DOI: 10.1105/tpc.114.123141] [Citation(s) in RCA: 152] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 04/12/2014] [Accepted: 04/22/2014] [Indexed: 05/17/2023]
Abstract
Rab GTPases serve as multifaceted organizers during vesicle trafficking. Rab7, a member of the Rab GTPase family, has been shown to perform various essential functions in endosome trafficking and in endosome-to-lysosome trafficking in mammalian systems. The Arabidopsis thaliana genome encodes eight putative Rab7 homologs; however, the detailed function and activation mechanism of Rab7 in plants remain unknown. Here, we demonstrate that Arabidopsis RABG3f, a member of the plant Rab7 small GTPase family, localizes to prevacuolar compartments (PVCs) and the tonoplast. The proper activation of Rab7 is essential for both PVC-to-vacuole trafficking and vacuole biogenesis. Expression of a dominant-negative Rab7 mutant (RABG3fT22N) induces the formation of enlarged PVCs and affects vacuole morphology in plant cells. We also identify Arabidopsis MON1 (MONENSIN SENSITIVITY1) and CCZ1 (CALCIUM CAFFEINE ZINC SENSITIVITY1) proteins as a dimeric complex that functions as the Rab7 guanine nucleotide exchange factor. The MON1-CCZ1 complex also serves as the Rab5 effector to mediate Rab5-to-Rab7 conversion on PVCs. Loss of functional MON1 causes the formation of enlarged Rab5-positive PVCs that are separated from Rab7-positive endosomes. Similar to the dominant-negative Rab7 mutant, the mon1 mutants show pleiotropic growth defects, fragmented vacuoles, and altered vacuolar trafficking. Thus, Rab7 activation by the MON1-CCZ1 complex is critical for vacuolar trafficking, vacuole biogenesis, and plant growth.
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Affiliation(s)
- Yong Cui
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Qiong Zhao
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Caiji Gao
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yu Ding
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yonglun Zeng
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Takashi Ueda
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Akihiko Nakano
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Liwen Jiang
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China
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38
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Abstract
The counterbalancing action of the endocytosis and secretory pathways maintains a dynamic equilibrium that regulates the composition of the plasma membrane, allowing it to maintain homeostasis and to change rapidly in response to alterations in the extracellular environment and/or intracellular metabolism. These pathways are intimately integrated with intercellular signaling systems and play critical roles in all cells. Studies in Caenorhabditis elegans have revealed diverse roles of membrane trafficking in physiology and development and have also provided molecular insight into the fundamental mechanisms that direct cargo sorting, vesicle budding, and membrane fisson and fusion. In this review, we summarize progress in understanding membrane trafficking mechanisms derived from work in C. elegans, focusing mainly on work done in non-neuronal cell-types, especially the germline, early embryo, coelomocytes, and intestine.
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Affiliation(s)
- Ken Sato
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan. ;
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39
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Delahaye JL, Foster OK, Vine A, Saxton DS, Curtin TP, Somhegyi H, Salesky R, Hermann GJ. Caenorhabditis elegans HOPS and CCZ-1 mediate trafficking to lysosome-related organelles independently of RAB-7 and SAND-1. Mol Biol Cell 2014; 25:1073-96. [PMID: 24501423 PMCID: PMC3967972 DOI: 10.1091/mbc.e13-09-0521] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
As early endosomes mature, the SAND-1/CCZ-1 complex acts as a guanine nucleotide exchange factor (GEF) for RAB-7 to promote the activity of its effector, HOPS, which facilitates late endosome-lysosome fusion and the consumption of AP-3-containing vesicles. We show that CCZ-1 and the HOPS complex are essential for the biogenesis of gut granules, cell type-specific, lysosome-related organelles (LROs) that coexist with conventional lysosomes in Caenorhabditis elegans intestinal cells. The HOPS subunit VPS-18 promotes the trafficking of gut granule proteins away from lysosomes and functions downstream of or in parallel to the AP-3 adaptor. CCZ-1 also acts independently of AP-3, and ccz-1 mutants mistraffic gut granule proteins. Our results indicate that SAND-1 does not participate in the formation of gut granules. In the absence of RAB-7 activity, gut granules are generated; however, their size and protein composition are subtly altered. These observations suggest that CCZ-1 acts in partnership with a protein other than SAND-1 as a GEF for an alternate Rab to promote gut granule biogenesis. Point mutations in GLO-1, a Rab32/38-related protein, predicted to increase spontaneous guanine nucleotide exchange, specifically suppress the loss of gut granules by ccz-1 and glo-3 mutants. GLO-3 is known to be required for gut granule formation and has homology to SAND-1/Mon1-related proteins, suggesting that CCZ-1 functions with GLO-3 upstream of the GLO-1 Rab, possibly as a GLO-1 GEF. These results support LRO formation occurring via processes similar to conventional lysosome biogenesis, albeit with key molecular differences.
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Affiliation(s)
- Jared L Delahaye
- Department of Biology, Lewis & Clark College, Portland, OR 97219 Program in Biochemistry and Molecular Biology, Lewis & Clark College, Portland, OR 97219
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40
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Girard E, Chmiest D, Fournier N, Johannes L, Paul JL, Vedie B, Lamaze C. Rab7 is functionally required for selective cargo sorting at the early endosome. Traffic 2014; 15:309-26. [PMID: 24329906 DOI: 10.1111/tra.12143] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 12/04/2013] [Accepted: 12/10/2013] [Indexed: 12/26/2022]
Abstract
The small GTPases of the Rab family act as a molecular switch regulating various aspects of membrane trafficking through the selective recruitment of effector proteins. Whereas Rab7 has been classically involved in the regulation of transport within the endolysosomal network, persistent controversy remains as to whether Rab7 also plays a role in earlier steps of endosomal trafficking. In this study, we show that Rab7 depletion or inactivation results in enlargement of both early and late endosomes. Rab7 depletion led to the retention of a significant fraction of internalized low-density lipoproteins (LDL) mainly in enlarged early endosomes (EE). As a result, LDL processing and the transcriptional regulation of sterol-sensitive genes were impaired. We found that Rab7 activity was also required for the sorting of the mannose-6-phosphate receptor, the interferon alpha-receptor and the Shiga toxin B-subunit. In contrast, epidermal growth factor (EGF) sorting at the EE or the recycling of transferrin and LDL-R were not affected by Rab7 depletion. Our findings demonstrate that in addition to regulating late endosomes (LE) to lysosomes transport, Rab7 plays a functional role in the selective sorting of distinct cargos at the EE and that the Rab5 to Rab7 exchange occurs early in the endosomal maturation process.
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Affiliation(s)
- Emmanuelle Girard
- AP-HP (Assistance Publique - Hôpitaux de Paris), Hôpital Européen Georges Pompidou, Service de Biochimie, 75015, Paris, France; Université Paris-Sud, EA 4529, UFR de Pharmacie, 92296, Châtenay-Malabry, France; CNRS UMR144, 75248 Paris cedex 05, France; Institut Curie, Centre de Recherche, Laboratoire Trafic, Signalisation et Ciblage Intracellulaires, 75248, Paris Cedex 05, France
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41
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N-glycosylation is required for secretion and mitosis in C. elegans. PLoS One 2013; 8:e63687. [PMID: 23691084 PMCID: PMC3653792 DOI: 10.1371/journal.pone.0063687] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 04/04/2013] [Indexed: 01/15/2023] Open
Abstract
N-glycosylation of proteins is an essential process, and N-glucans serve as important beacons in protein folding and ER associated degradation. More importantly, N-glycosylation increases the structural repertoire of proteins because the addition of the N-glucan on proteins will serve as a base for further sugar additions in the Golgi apparatus, and hence complex three-dimensional structures can be build. N-glycosylation is mediated by the ER-resident OST complex, which is essential throughout eukaryotes. Partial knockdown of conserved OST complex members, such as C. elegans RIBO-1, led to an embryonic lethal phenotype. Although the ER morphology was not grossly altered in ribo-1(RNAi) oocytes and embryos, secretion of yolk and of the yolk receptor RME-2 was perturbed in those worms. Perhaps as a consequence of reduced arrival of N-glycosylated proteins at the plasma membrane, cytokinesis occurred less efficiently leading to multinuclear cells. Unexpectedly, we detected a chromosome segregation defect in ribo-1(RNAi) embryos suggesting an essential role of at least one N-glycosylated protein in metaphase-anaphase transition.
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42
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Sasaki A, Nakae I, Nagasawa M, Hashimoto K, Abe F, Saito K, Fukuyama M, Gengyo-Ando K, Mitani S, Katada T, Kontani K. Arl8/ARL-8 functions in apoptotic cell removal by mediating phagolysosome formation in Caenorhabditis elegans. Mol Biol Cell 2013; 24:1584-92. [PMID: 23485564 PMCID: PMC3655818 DOI: 10.1091/mbc.e12-08-0628] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 02/19/2013] [Accepted: 03/07/2013] [Indexed: 12/29/2022] Open
Abstract
Efficient clearance of apoptotic cells by phagocytes is important for development, tissue homeostasis, and the prevention of autoimmune responses. Phagosomes containing apoptotic cells undergo acidification and mature from Rab5-positive early to Rab7-positive late stages. Phagosomes finally fuse with lysosomes to form phagolysosomes, which degrade apoptotic cells; however, the molecular mechanism underlying phagosome-lysosome fusion is not fully understood. Here we show that the Caenorhabditis elegans Arf-like small GTPase Arl8 (ARL-8) is involved in phagolysosome formation and is required for the efficient removal of apoptotic cells. Loss of function of arl-8 results in the accumulation of apoptotic germ cells. Both the engulfment of the apoptotic cells by surrounding somatic sheath cells and the phagosomal maturation from RAB-5- to RAB-7-positive stages occur in arl-8 mutants. However, the phagosomes fail to fuse with lysosomes in the arl-8 mutants, leading to the accumulation of RAB-7-positive phagosomes and the delayed degradation of apoptotic cells. ARL-8 localizes primarily to lysosomes and physically interacts with the homotypic fusion and protein sorting complex component VPS-41. Collectively our findings reveal that ARL-8 facilitates apoptotic cell removal in vivo by mediating phagosome-lysosome fusion during phagocytosis.
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Affiliation(s)
- Ayaka Sasaki
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Isei Nakae
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Maya Nagasawa
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Keisuke Hashimoto
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Fumiko Abe
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kota Saito
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masamitsu Fukuyama
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Keiko Gengyo-Ando
- Department of Physiology, School of Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Shohei Mitani
- Department of Physiology, School of Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Toshiaki Katada
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kenji Kontani
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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43
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Solinger JA, Spang A. Tethering complexes in the endocytic pathway: CORVET and HOPS. FEBS J 2013; 280:2743-57. [PMID: 23351085 DOI: 10.1111/febs.12151] [Citation(s) in RCA: 138] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 01/10/2013] [Accepted: 01/23/2013] [Indexed: 12/21/2022]
Abstract
Endocytosis describes the processes by which proteins, peptides and solutes, and also pathogens, enter the cell. Endocytosed material progresses to endosomes. Genetic studies in yeast, worms, flies and mammals have identified a set of universally conserved proteins that are essential for early-to-late endosome transition and lysosome biogenesis, and for endolysosomal trafficking pathways, including autophagy. The two Vps-C complexes CORVET (class C core vacuole/endosome tethering) and HOPS (homotypic fusion and vacuole protein sorting) perform diverse biochemical functions in endocytosis: they tether membranes, interact with Rab GTPases, activate and proof-read SNARE assembly to drive membrane fusion, and possibly attach endosomes to the cytoskeleton. In addition, several of the CORVET and HOPS subunits have diversified in metazoans, and probably form additional specialized complexes to accomodate the higher complexity of trafficking pathways in these cells. Recent studies offer new insights into the complex relationships between CORVET and HOPS complexes and other factors of the endolysosomal pathway. Interactions with V-ATPase, the ESCRT machinery, phosphoinositides, the cytoskeleton and the Rab switch suggest an intricate cooperative network for endosome maturation. Accumulating evidence supports the view that endosomal tethering complexes implement a regulatory logic that governs endomembrane identity and dynamics.
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44
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Yousefian J, Troost T, Grawe F, Sasamura T, Fortini M, Klein T. Dmon1 controls recruitment of Rab7 to maturing endosomes in Drosophila. J Cell Sci 2013; 126:1583-94. [PMID: 23418349 DOI: 10.1242/jcs.114934] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The small GTPases Rab5 and Rab7 are important organisers of endosome formation and maturation. In addition, they orchestrate the trafficking of cargo through the endosomal pathway. A crucial event during maturation of endosomes is the replacement of the early organiser Rab5 with the late organiser Rab7 in a process called Rab conversion. Rab conversion is a prerequisite for late events, chief among them the fusion of matured endosomes with the lysosome. Recent work identifies members of the Sand1/Mon1 protein family as crucial factors during this process. Here, we present an analysis of the function of the Drosophila ortholog of mon1/sand1, Dmon1. We found that loss of function of Dmon1 results in an enlargement of maturing endosomes and loss of their association with Rab7. The enlarged endosomes contain Notch and other trans-membrane proteins as cargo. We report the first electron microscopy analysis of Dmon1 cells in a metazoan and extend the analysis of the endosomes in mutant cells. Our results suggest that the phenotype can be explained by the loss of function of Rab7. Moreover, the endosomes of Dmon1 cells mature normally in many aspects, despite the loss of association with Rab7. Surprisingly, we did not observe overactive or ectopic signalling through receptors such as Notch and RTKs in Dmon1 mutant cells, as would have been expected because of the accumulation of receptors in the maturing endosomes of these cells. This was the case even when receptor uptake into intraluminal vesicles was suppressed.
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Affiliation(s)
- Jahan Yousefian
- Institut für Genetik, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
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45
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Hanna M, Wang L, Audhya A. Worming our way in and out of the Caenorhabditis elegans germline and developing embryo. Traffic 2013; 14:471-8. [PMID: 23331906 DOI: 10.1111/tra.12044] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 01/11/2013] [Accepted: 01/17/2013] [Indexed: 12/18/2022]
Abstract
The germline and embryo of the nematode Caenorhabditis elegans have emerged as powerful model systems to study membrane dynamics in an intact, developing animal. In large part, this is due to the architecture of the reproductive system, which necessitates de novo membrane and organelle biogenesis within the stem cell niche to drive compartmentalization throughout the gonad syncytium. Additionally, membrane reorganization events during oocyte maturation and fertilization have been demonstrated to be highly stereotypic, facilitating the development of quantitative assays to measure the impact of perturbations on protein transport. This review will focus on regulatory mechanisms that govern protein trafficking, which have been elucidated using a combination of C. elegans genetics, biochemistry and high-resolution microscopy. Collectively, studies using the simple worm highlight an important niche that the organism holds to define new pathways that regulate vesicle transport, many of which appear to be absent in unicellular systems but remain highly conserved in mammals.
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Affiliation(s)
- Michael Hanna
- Department of Biomolecular Chemistry, University of Wisconsin-Madison Medical School, 440 Henry Mall, Madison, WI 53706, USA
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46
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Gao HM, Liu XG, Shi HB, Lu JP, Yang J, Lin FC, Liu XH. MoMon1 is required for vacuolar assembly, conidiogenesis and pathogenicity in the rice blast fungus Magnaporthe oryzae. Res Microbiol 2013; 164:300-9. [PMID: 23376292 DOI: 10.1016/j.resmic.2013.01.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 12/26/2012] [Indexed: 01/07/2023]
Abstract
Mon1 protein is involved in cytoplasm-to-vacuole trafficking, vacuolar morphology and autophagy, and is required for homotypic vacuole fusion in Saccharomyces cerevisiae. Here we identify MoMON1 from Magnaporthe oryzae as an ortholog of S. cerevisiae MON1, essential for the morphology of the vacuole and vesicle fusion. Target gene deletion of MoMON1 resulted in accumulation of small punctuate vacuoles in the hypha and hypersensitivity to monensin, an antibiotic that blocks intracellular protein transport. The ΔMomon1 mutant exhibited significantly reduced aerial hyphal development and poor conidiation. Conidia of ΔMomon1 were able to differentiate appressoria. However, ΔMomon1 was non-pathogenic on rice leaves, even after wound inoculation. In addition, ΔMomon1 was slightly hypersensitive to Congo red and SDS, but not to cell wall degrading enzymes, suggesting significant alterations in its cell wall. The autophagy process was blocked in the ΔMomon1 mutant. Taken together, our results suggest that MoMON1 has an essential function in vacuolar assembly, autophagy, fungal development and pathogenicity in M. oryzae.
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Affiliation(s)
- Hui-Min Gao
- State Key Laboratory for Rice Biology, Biotechnology Institute, Zhejiang University, Hangzhou 310058, China
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47
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Hermann GJ, Scavarda E, Weis AM, Saxton DS, Thomas LL, Salesky R, Somhegyi H, Curtin TP, Barrett A, Foster OK, Vine A, Erlich K, Kwan E, Rabbitts BM, Warren K. C. elegans BLOC-1 functions in trafficking to lysosome-related gut granules. PLoS One 2012; 7:e43043. [PMID: 22916203 PMCID: PMC3419718 DOI: 10.1371/journal.pone.0043043] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Accepted: 07/16/2012] [Indexed: 12/18/2022] Open
Abstract
The human disease Hermansky-Pudlak syndrome results from defective biogenesis of lysosome-related organelles (LROs) and can be caused by mutations in subunits of the BLOC-1 complex. Here we show that C. elegans glo-2 and snpn-1, despite relatively low levels of amino acid identity, encode Pallidin and Snapin BLOC-1 subunit homologues, respectively. BLOC-1 subunit interactions involving Pallidin and Snapin were conserved for GLO-2 and SNPN-1. Mutations in glo-2 and snpn-1,or RNAi targeting 5 other BLOC-1 subunit homologues in a genetic background sensitized for glo-2 function, led to defects in the biogenesis of lysosome-related gut granules. These results indicate that the BLOC-1 complex is conserved in C. elegans. To address the function of C. elegans BLOC-1, we assessed the intracellular sorting of CDF-2::GFP, LMP-1, and PGP-2 to gut granules. We validated their utility by analyzing their mislocalization in intestinal cells lacking the function of AP-3, which participates in an evolutionarily conserved sorting pathway to LROs. BLOC-1(−) intestinal cells missorted gut granule cargo to the plasma membrane and conventional lysosomes and did not have obviously altered function or morphology of organelles composing the conventional lysosome protein sorting pathway. Double mutant analysis and comparison of AP-3(−) and BLOC-1(−) phenotypes revealed that BLOC-1 has some functions independent of the AP-3 adaptor complex in trafficking to gut granules. We discuss similarities and differences of BLOC-1 activity in the biogenesis of gut granules as compared to mammalian melanosomes, where BLOC-1 has been most extensively studied for its role in sorting to LROs. Our work opens up the opportunity to address the function of this poorly understood complex in cell and organismal physiology using the genetic approaches available in C. elegans.
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Affiliation(s)
- Greg J Hermann
- Department of Biology, Lewis and Clark College, Portland, Oregon, USA.
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48
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Chao WS, Doğramaci M, Foley ME, Horvath DP, Anderson JV. Selection and validation of endogenous reference genes for qRT-PCR analysis in leafy spurge (Euphorbia esula). PLoS One 2012; 7:e42839. [PMID: 22916167 PMCID: PMC3419244 DOI: 10.1371/journal.pone.0042839] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 07/12/2012] [Indexed: 11/18/2022] Open
Abstract
Quantitative real-time polymerase chain reaction (qRT-PCR) is the most important tool in measuring levels of gene expression due to its accuracy, specificity, and sensitivity. However, the accuracy of qRT-PCR analysis strongly depends on transcript normalization using stably expressed reference genes. The aim of this study was to find internal reference genes for qRT-PCR analysis in various experimental conditions for seed, adventitious underground bud, and other organs of leafy spurge. Eleven candidate reference genes (BAM4, PU1, TRP-like, FRO1, ORE9, BAM1, SEU, ARF2, KAPP, ZTL, and MPK4) were selected from among 171 genes based on expression stabilities during seed germination and bud growth. The other ten candidate reference genes were selected from three different sources: (1) 3 stably expressed leafy spurge genes (60S, bZIP21, and MD-100) identified from the analyses of leafy spurge microarray data; (2) 3 orthologs of Arabidopsis “general purpose” traditional reference genes (GAPDH_1, GAPDH_2, and UBC); and (3) 4 orthologs of Arabidopsis stably expressed genes (UBC9, SAND, PTB, and F-box) identified from Affymetrix ATH1 whole-genome GeneChip studies. The expression stabilities of these 21 genes were ranked based on the CT values of 72 samples using four different computation programs including geNorm, Normfinder, BestKeeper, and the comparative ΔCT method. Our analyses revealed SAND, PTB, ORE9, and ARF2 to be the most appropriate reference genes for accurate normalization of gene expression data. Since SAND and PTB were obtained from 4 orthologs of Arabidopsis, while ORE9 and ARF2 were selected from 171 leafy spurge genes, it was more efficient to identify good reference genes from the orthologs of other plant species that were known to be stably expressed than that of randomly testing endogenous genes. Nevertheless, the two newly identified leafy spurge genes, ORE9 and ARF2, can serve as orthologous candidates in the search for reference genes from other plant species.
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Affiliation(s)
- Wun S Chao
- United States Department of Agriculture-Agricultural Research Service, Biosciences Research Lab, Sunflower and Plant Biology Research Unit, Fargo, North Dakota, USA.
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49
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Pedersen NM, Raiborg C, Brech A, Skarpen E, Roxrud I, Platta HW, Liestøl K, Stenmark H. The PtdIns3P-binding protein Phafin 2 mediates epidermal growth factor receptor degradation by promoting endosome fusion. Traffic 2012; 13:1547-63. [PMID: 22816767 DOI: 10.1111/j.1600-0854.2012.01400.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 07/17/2012] [Accepted: 07/20/2012] [Indexed: 12/16/2022]
Abstract
Phosphatidylinositol 3-phosphate (PtdIns3P) orchestrates endosomal cargo transport, fusion and motility by recruiting FYVE or PX domain-containing effector proteins to endosomal membranes. In an attempt to discover novel PtdIns3P effectors involved in the termination of growth factor receptor signalling, we performed an siRNA screen for epidermal growth factor (EGF) degradation, targeting FYVE and PX domain proteins in the human proteome. This screen identified several potential regulators of EGF degradation, including HRS (used as positive control), PX kinase, MTMR4 and Phafin2/PLEKHF2. As Phafin2 has not previously been shown to be required for EGF receptor (EGFR) degradation, we performed further functional studies on this protein. Loss of Phafin2 was found to decrease early endosome size, whereas overexpression of Phafin2 resulted in enlarged endosomes. Moreover, both the EGFR and the fluid-phase marker dextran were retained in abnormally small endosomes in Phafin2-depleted cells. In yeast two-hybrid analysis we identified Phafin2 as a novel interactor of the endosomal-tethering protein EEA1, and Phafin2 colocalized strongly with EEA1 in microdomains of the endosome membrane. Our results suggest that Phafin2 controls receptor trafficking and fluid-phase transport through early endosomes by facilitating endosome fusion in concert with EEA1.
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Affiliation(s)
- Nina Marie Pedersen
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, N-0310, Oslo, Norway
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50
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Bagley DC, Paradkar PN, Kaplan J, Ward DM. Mon1a protein acts in trafficking through the secretory apparatus. J Biol Chem 2012; 287:25577-88. [PMID: 22665492 DOI: 10.1074/jbc.m112.354043] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Mon1a was originally identified as a modifier gene of vesicular traffic, as a mutant Mon1a allele resulted in increased localization of cell surface proteins, whereas reduced levels of Mon1a showed decreased secretory activity. Here we show that Mon1a affects different steps in the secretory pathway including endoplasmic reticulum-to-Golgi traffic. siRNA-dependent reduction of Mon1a levels resulted in a delay in the reformation of the Golgi apparatus after Brefeldin A treatment. Endoglycosidase H treatment of ts045VSVG-GFP confirmed that knockdown of Mon1a delayed endoplasmic reticulum-to-Golgi trafficking. Reductions in Mon1a also resulted in delayed trafficking from Golgi to the plasma membrane. Immunoprecipitation and mass spectrometry analysis showed that Mon1a associates with dynein intermediate chain. Reductions in Mon1a or dynein altered steady state Golgi morphology. Reductions in Mon1a delayed formation of ERGIC-53-positive vesicles, whereas reductions in dynein did not affect vesicle formation. These data provide strong evidence for a role for Mon1a in anterograde trafficking through the secretory apparatus.
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Affiliation(s)
- Dustin C Bagley
- Department of Pathology, School of Medicine, University of Utah, Salt Lake City, Utah 84132, USA
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